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Zn-ion energy storage devices employing hydrogel electrolytes are considered as promising candidates for flexible and wearable electronics applications. This is because of their safe nature, low cost, and good mechanical characteristics. However, conventional hydrogel electrolytes face limitation at subzero temperatures. Herein, we report an antifreezing, safe, and nontoxic gel electrolyte based on the poly­(vinyl alcohol) (PVA)/Zn/ethylene glycol system. The optimal gel electrolyte membrane exhibits a high ionic conductivity (15.03 mS cm–1 at room temperature) and promising antifreezing performance (9.05 mS cm–1 at −20 °C and 3.53 mS cm–1 at −40 °C). Moreover, the antifreezing gel electrolyte can suppress the growth of Zn dendrites to display a uniform Zn plating/stripping behavior. Also, a flexible antifreezing Zn-ion hybrid supercapacitor fabricated with the optimum antifreezing gel electrolyte membrane exhibits excellent electrochemical properties. The supercapacitor possesses a high specific capacity of 247.7 F g–1 at room temperature under a high working voltage of 2 V. It also displays an outstanding cyclic stability at room temperature. Moreover, the supercapacitor shows an extraordinary electrochemical behavior and cyclic stability over up to 30 000 cycles at −20 °C under a current load of 5 A g–1, demonstrating its outstanding low-temperature electrochemical performance. Besides, the antifreezing supercapacitor device also offers high flexibility under different deformation conditions. Therefore, it is believed that this work provides a simplistic method of realizing the application of flexible antifreezing Zn-ion energy storage devices in a subzero-temperature environment.

The present study describes preparation of doped activated carbon (NAC), employing waste orange peel as carbon source, melamine as nitrogen dopant and KOH as activating agent. The prepared NAC samples were textually characterized using the techniques of surface area and pore size analyzer, scanning electron microscopy (SEM), x-ray diffraction (XRD) and Raman spectroscopy. As evident from characterization results, the synthesized NAC materials own porous structure and offers high surface area , and pore volume . Such useful characteristics of NAC indicate its suitability as electrode for supercapacitors. Electrochemical performance of NAC material was evaluated in 6 M KOH aqueous solution, employing the standard electrochemical avenues of analysis. It was found that synthesized NAC sample exhibits high specific capacitance , specific energy and specific power at current load of . The better electrochemical performance of the NAC is probably due to enhanced surface area and availability of nitrogen functional groups. Thus, the porous structure and nitrogen-doping characteristics make NAC a potential electrode material for applications in the field of supercapacitors.

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